This invention relates generally to apparatus for brewing coffee, and more particularly to improved coffee makers adapted to brew coffee quickly and efficiently without boiling of the brew to produce an aromatic beverage of high quality.
The simplest technique for brewing coffee is the so-called pot method in which a charge of ground coffee is deposited in a pot of boiling water and allowed to steep until a brew of the proper concentration is produced. This traditional technique has certain drawbacks, some of which arise from the nature of ground, roasted coffee. Roasted coffee contains about 1 to 2% of alkaloid caffein, and while it also contains glucose, dextrin and protein, its characteristic aroma is due primarily to oily substances known as caffeol.
In making pot coffee, one must wait for the coffee grounds to settle, otherwise the grounds will remain dispersed in the brew and the beverage will be unpleasant to the taste. On the other hand, since the grounds are not separated from the liquid, a point may be reached where coffee concentration is excessive or the oils boil out to impart a disagreeable flavor to the brew. Thus the quality of pot coffee is difficult to control.
The drip method generally produces coffee of better quality than the pot method, for it makes use of a double-cup container whose upper section holds the charge of ground coffee. In the drip method, boiling water is poured over the coffee grounds and the resultant brew trickles through the pores in the bottom of the upper section into the lower section of the container. The disadvantage of the drip method is that it is relatively slow and the trickle of beverage may be impeded or altogether arrested should the wet coffee grounds pack together and become impermeable.
The filter method is similar to the drip method and produces a brew of good quality, except that the coffee grounds are deposited in a funnel-shaped paper filter, permeable only to the beverage. This method is also quite slow, for the coffee grounds tend to clog the filter and no pressure is developed to accelerate the slow trickle of the beverage through the filter. The well-known coffee percolator produces a coffee brew more quickly. But since in this technique the boiling beverage is recirculated through the coffee grounds, the aromatic oils are volatilized and the resultant beverage is relatively flat.
Thus when brewing quickly with recirculated boiling water as in a percolator, or with live steam as in an expresso machine, the aromatic oils are volatilized and the brew is rendered flat, whereas when brewing with water brought to a boil as in the drip or filter method, the coffee is of better quality but the brewing process is much slower. Hence, those known techniques which are slow produce a coffee brew of good quality and those which are fast produce an inferior beverage.
With a view to overcoming the drawbacks inherent in existing techniques, the Kasakoff patent 3,348,469 discloses a coffee brewer in which a concentrated coffee brew is produced in a perforated container that floats upside down within a pot of boiling water. The floating container is subjected to steam which enters the container through filtered perforations therein, the steam serving to express the brew into the boiling pot water. While this technique produces a superior brew in no more than about a minute, it involves a relatively complicated procedure.